a=input("一串数字")
list=[]
for i in range(1,len(a)+1):
    list.append(int(a[i-1]))
#print(list)
i=1
#print(list[i])
for i in range(1,len(a)):
    if list[i - 1] < list[i]:
        x = list[i - 1]
        y = list[i]

        list[i - 1] = y
        list[i] = x
#print(list)
x=''
for i in list:
    x=x+str(i)
print(x)